In the petroleum refining industry, the role of the catalytic cracking process generally is to crack a hydrocarbon oil by bringing it into contact with a catalyst to thereby produce cracked gasoline in high yield.
As the feedstock oil, vacuum gas oil (VGO) has mostly been used conventionally.
Recently however, the crude oil situation and the trend of the petroleum product market have led to a growing desire for a process in which bottoms (heavy distillate) obtained in an atmospheric or vacuum distillation (hereinafter referred to as bottoms) are also used as the feedstock oil to be cracked and light cracked oil fractions (hereinafter referred to as LCO) are increased simultaneously with the gasoline fraction.
Catalysts designed for attaining improved conversion of bottoms have been proposed which include a catalyst comprising a mixture of silica-alumina, .gamma.-alumina, boehmite, or the like as an inorganic oxide matrix which is one of the catalyst components and stabilized zeolite Y, and a catalyst comprising a mixture of an alumina-magnesia matrix and a crystalline aluminosilicate (see JP-A-58-163439 and JP-A-1-111446). (The term "JP-A" as used herein means an "unexamined published Japanese patent application".)
On the other hand, the present inventors proposed a crystalline aluminosilicate which has a specific structure obtained by applying a certain thermal load to a specific stabilized zeolite Y (JP-A-4-59616).